Navigating Indiana’s New Storm‑Water Rules: What Developers Need to Know for 2025
Indiana’s storm‑water landscape changed in 2021 with the Construction Stormwater General Permit (CSGP) and is changing again in 2025 with a new Industrial Stormwater General Permit (ISGP) Indiana Government KERAMIDA Inc.. Here’s the quick‑start guide.
1. Know Which Permit You Fall Under
- CSGP – Land disturbance ≥ 1 acre. Focuses on erosion control and sediment runoff
Indiana Government - ISGP – Regulates discharges from industrial facilities, including some prefabrication yards and concrete batch plants.
2. Update Your SWPPP—Soon
The draft ISGP adds sector‑specific benchmark limits and more frequent sampling. Start revising your Stormwater Pollution Prevention Plan now so it’s ready when IDEM finalizes the permit.
3. New Digital Submittals
Permits, inspections, and corrective actions will be tracked in IDEM’s nSITE Explorer. Assign a project admin early to avoid login bottlenecks.
4. Design Implications
- Temporary BMPs: Expect higher silt‑fence density on slopes > 10 %.
- Post‑Construction BMPs: Bio‑swales and underground detention tanks are now the preferred methods to meet water‑quality volume.
- Record Drawings: As‑builts must show actual BMP dimensions within ±10 % tolerance.
5. Fines Are Real
IDEM issued more than 120 NOVs in 2024 related to CSGP non‑compliance; average settlement: $28,000.
Action Checklist
- Confirm which permit applies to your next project.
- Engage a civil engineer to model post‑construction flows with the new criteria.
- Schedule SWPPP training for site superintendents before mobilization.
Need help interpreting the new rules? Start a Conversation with Bedrock—our pre‑con team has navigated dozens of recent CSGP approvals and can keep your schedule moving while staying compliant.